Gelatin coating compositions



tent

Patented July 11, 1961 ice 2,992,108 GELATIN COATING COMPOSITIONSWilliam J. Knox, Jr., and John Stenberg, Rochester, N.Y., assignors toEastman Kodak Company, Rochester, N .Y., a corporation of New Jersey NoDrawing. Filed Oct. 21, 1957, Ser. No. 691,125 Claims. (Cl. 96-85) Thisinvention relates to gelatin coating solutions particularly forphotographic purposes and the employment of those solutions in themanufacture of photographic products.

In the application of gelatin coating compositions such as ofphotographic emulsions or of protective coatings, to film base or topaper the addition of a coating aid such as saponin to the coatingcomposition permits the application of a smooth, even coating.Furthermore, the presence of saponin in an emulsion coating enables theemulsion while wet and in a chilled, set condition to be overcoated witha protective gelatin coating (weton-wet coating process).

If saponin or some other suitable coating aid is omitted from a coatingcomposition which is applied to film base or paper as a single layerthereon (wet-on-dry process) the coating thus laid down is prone todevelop deficiencies such as the presence of repellencies, mottle andstreakiness and a subsequent application of a protective gelatin coatingthereover at reasonable speeds by a wet-on-wet coating process will beimpossible.

Saponin although quite useful as a coating aid in applying gelatinlayers in preparing photographic products, is nevertheless a naturallyoccurring substance and may show decided variations in quality frombatch to batch. These variations are such that some batches of saponinmay cause fog increase or a change in photographic sensitivity or maycause no improvement in the coating properties of the system to whichthe saponin has been added. Because of these variations of the qualityof various saponins, it is preferred that synthetic surfactants whichare reproducible from batch to batch both in chemical composition and inbehavior, be employed as coating aids in gelatin coating compositionseither alone or in admixture with other suitable coating aids.

Coating techniques have been developed for the application of gelatinlayers which involve the simultaneous application of two or more gelatinlayers to film base or to paper. In those techniques saponin has oftenbeen found to be not particularly satisfactory. In those procedureswhere saponin has been used, the ratio of the bulk concentrations ofsaponin in the various layers appears to be critical and frequentlyproducts free from streaks and other defects such as skips andrepellencies are difiicult to obtain when saponin has been employed asthe coating aid. This is also true of many other surfactant materialswhich have been considered.

This invention has for one object to provide an improved method forapplying aqueous gelatin coatings. Another object of our invention is toprovide gelatin coating compositions which can be applied to supportstherefor without exhibiting the disadvantages which have been found inattempts to coat previous gelatin coating compositions. A further objectof our invention is to provide an improved coating procedure whereby anundried first coating of gelatin may be followed by further gelatincoatings thereon with good results. Other objects of our invention willappear herein.

We have found surfactants which, when used as coating aids in variousphotographic emulsions and gelatin coating compositions, are effectivein at least 2 if not all 3 of the following particulars: (1) incontrolling repellency and other coating deficiencies (2) in enablinghigh speed wet-on-wet coating and (3) in enabling the satisfactorysimultaneous application to fihn base or paper of two or more gelatinlayers independent of the concentration ratio of the surfactants in anytwo contiguous layers. These materials have indicated their superiorityto saponin as coating aids in the preparation of photographic productsinvolving the application of gelatin layers therein.

We have found that certain related compounds having both amide andcarboxylic acid groups therein have shown themselves to be very usefulas coating aids in the preparation of coating compositions. Thesecompounds are prepared by the reaction of high molecular weight amineswith reagents which will supply carboxylic acid groups to the resultingproduct. One class of surfactant materials which has been found to beuseful in this connection has the structural formula:

CH CONHR OHCO ONa SOaNa in which formula R is an alkyl group of 8 to 18carbon atoms or some other hydrophobic like radical such as oleyl,abietyl or alkyl and having a molecular weight equivalent to at least 12carbon atoms. Examples of long chain alkyl groups of 8 to 18 carbonatoms straight or branch chain are octyl, laury-l, octadecyl ortrimethyl nonyl. An example of an alkylaryl group is dodecyl phenyl. Inthe above formula Na can be replaced with some other alkali radical suchas potassium, lithium or ammonium. The preparation of compounds of thistype is described in US. Patent No. 2,252,401 of Alphonse O. Jaeger.

Another class of compounds of this type the members of which are usefulfor incorporating into gelatin coating compositions as coating aids arethose having the following formula:

CHrCO OX CHCO OX CHzOON XOaSOHGO OX R in which R represents any of thegroups which are represented by R in the preceding formula and X is analkali substituent such as NH Na, K or Li. The preparation of compoundsof this type is described in US. Patent No. 2,438,092. For example, asuitable coating aid of this type may be prepared by the following procedure using a high molecular weight amine in that procedure:

To a solution of 71 parts of laurylamine in 250 parts of t-butanol wasadded 65.5 parts of diethyl maleate.-

The mass was allowed to stand for 72 hours at room temperature and wasthen warmed to 60 C. and 39.5 parts of maleic 'anhydride was added insmall portions with stirring. The solution was stirred for one hour at90 C. to complete the acylation. The solution was then slowly pouredwith stirring into a hot solution of 50 parts of sodium sulfite in 188parts of distilled water. Heating was continued for 15 minutes. Theresulting clear solution was evaporated to dryness at a reducedpressure. The residue was dissolved in a liter of absolute alcohol andadded to a liter of alcohol to which had been added a solution of 31parts of sodium hydroxide in 60 parts of distilled water. A pinkishsolid separated which lightened in color on stirring for several hoursin a 60 bath. After cooling, the solid material was collected, washedwith ethyl ether and dried. The coating aid was obtained in the form ofa white powdery solid.

Another group of the compounds of this type are analogues of thepreceding, the preparation of which involves adding the amine to diethylmaleate, acylating the product with maleic anhydride and hydrolyzing theproduct thus obtained. These compounds have the following formula:

C170 CH=CHC OX RN-CHGOOX OHrCOOX in which R is a long chain alkyl of.8-18 carbon atoms, an alkyl aryl group of an abietyl group such vashave been referred to previously as being represented by R in theformulas herein. X represents Na, K, Li, or NH These compounds areprepared as described in U.S. Patent No. 2,438,092. The followingexample illustrates the preparation of one of these compounds:

65.5 parts of diethylmaleate was mixed with a solution of 71 parts oflaurylamine in 125 parts of tertiary butanol. The mixture was allowed tostand for three days at room temperature. The solution was then warmedto 60 C. and 39.5 parts of maleic anhydride was added in small portionswith stirring. The solution was heated to 85-90 C. and maintainedthereat for an hour to complete the acylation whereupon the mass wasevaporated to dryness at reduced pressure. The residue was dissolved in500 parts of ethanol and was added to 1000 parts of ethanol containing asolution of 48 parts of sodium hydroxide in 100 parts of Water. The masswas stirred for two hours at 60 C. A solid was collected and the coatingaid was obtained by drying this material to a fine powder.

In the use of the gelatin coating compositions in accordance with ourinvention, if a film base is to be coated, it may be composed of any ofthe usual conventional film base materials. This may be a sheet ofcellulose nitrate, or of an organic acid ester of cellulose such ascellulose acetate, cellulose acetate propionate or cellulose acetatebutyrate. It is often desirable first to apply a subbing layer to thecellulose ester base to facilitate adhesion of the photographic emulsionthereto; this practice of subbing being well known in the art. As forthe photographic paper a description thereof is found in Kodak DataBook, 5th edition, Kodak Papers, pages 3 and 4. A base material of thetype described there would preferably be employed for preparingphotographic paper in accordance with the present invention.

The coating procedure outlined may comprise any of the standardprocedures employed in the industry. As an instance of such procedure,paper base to be coated is passed through a trough or other reservoirwhereby a coating is applied to the paper base. The coating is appliedin greater thickness than desired and the surface is then subjected tothe action of some leveling means such as a doctor blade or an air brushwhich causes run back of the coating composition and results in an evensurface. In some cases it may be desirable to apply several coatingssimultaneously in the manner described in US. Patent No. 2,761,791 of T.A. Russell. In some cases the coating method may involve a hoppertechnique in which the thickness of the layer is regulated by the rateat which the coating composition is deposited upon the base which ismoved along adjacent thereto. We have found that the coating aids inaccordance with our invention are effective when used in gelatincompositions over a wide range such as from as little as .001%, based onthe weight of the gelatin, up to as much as 5 or even more on thatbasis. We have found that the presence of excessive coating aid asdescribed herein causes no discoloration or the like in coatingoperations and therefore there is no upper limit which can be regardedas critical as amounts of coating aid even up as much as 50% of theweight of the gelatin can be employed even though the economics of thecoating process makes proportions of this order impractical. Thefollowing examples illustrate coating procedures employing compositionsin accordance with our invention:

Example 1 A gelatin silver halide emulsion was applied to paper in ahopper type coating operation which emulsion contained various amountsof surfactant; The surfactant employed unless otherwise designated wasN-oc-tadecyl disodium sulfosuccinamate. This coating operation wascarried out at normal coating speed. This coating aid was employed inamounts from 0.13 gram to 1 gram per pound of emulsion. A product whichwas free from streaks or coating defects was obtained.

Surfactant Sample No. Concentra- Repellencies Photograph tion (gm/Projection 0.00 0 O.K Sap onin r Standard 0 O.K P 0.13 1 O.K 0.25 O O.K0. 5 0 O.K

Example 2 There was applied to paper simultaneously a layer of silverhalide gelatin emulsion and a clear gelatin overcoating using as thecoating aid N-octadecyl disodium sulfosuccinamate. The results obtainedwere as follows:

Surfactant Surfactant Photo- Gone. in Gene. in Repclgraph Pro- EmulsionOvercoat lencies jection -I (a /1b.)

0. l3 0. l3 0 O.K. 0. 25 0; 13 0 O.K. 0. 5 0. 13 0 O.K. 1. 0 0. l3 0O.K. O. 13 0. 25' 0 O.K. 0. 25 0. 25 0 O.K. 6. 5 0. 25 0 O .K. 1.0 0. 250 O.K. 0. 13 0. 50 0 O.K. 0. 25 0. 5 0 O.K. 0. 5 0. 5 O O.K. 1. 0 0. 5 0O .K. 0. l3 1. 0 0 O.K. 0. 25 1. 0 0 O.K. 0. 5 l. 0 0 O K. 1. 0 l. 0 0 O.K.

Example 3 A wet-on-wet coating operation involving X-ray type silverhalide emulsion and gelatin overcoating was run. N-octadecyldisodiumsulfosuccinamate was used at the rate of 1 gram to 2.5 pounds in theemulsion and 1 gram to 7.7 pounds in the overcoating over the emulsionlayer. The overcoat was applied to the wet emulsion layer by a hoppertechnique using normal coating speed. In this wet-on-wet coatingprocedure the results obtained were excel-lent.

Example4 A run was carried out similar to that in the preceding exampleexcept that the lauryl analogue was used as the coating aid. Similarexcellent wet-on-wet coating results were obtained.

Example 5 A gelatin silver halide photographic emulsion was applied topaper on a wet-on-dry application procedure using a knife technique.Normal coating speed was used. The surfactant which was employed in theemulsion composition was tetra sodium N-(1,2 dicarboxyethyl)-N-octadecyl sulf osuccinamat'e. The concentration of surfactant and theresults obtained were as follows:

Surfactant Repellencles Photographic Concentration (7.5 sq. ft.)Properties 0.00 2 O.K. 0.13 3 OK. 0.25 O.K. 0.5 0 OK. 1.0 0 O.K.

Example 6 A gelatin-silver halide emulsion and a clear gelatin overcoatwere applied simultaneously to paper support by a hopper technique inwhich tetra sodium N-(1,2 dicarboxyethyl) N-octadecyl sulfosuccinamatewas employed as the surfactant in both layers. The proportions used andthe results obtained in the finished products were as follows:

Surfactant Surfactant Gone. in Gone. in Repcllencies Emulsion Overcoat(7.5 sq. ft.)

(is-l s-/ 0. 13 0. l3 0 0. 25 0. l3 0 0. 5 07 13 1 1. 0 0. 13 0 0. 13 O.25 0 0. 25 O. 25 0 0. 5 0. 25 0 1. 0 0. 25 0 0. l3 0. 50 0 0. 25 0. 50 00. 50 O. 50 0 1. 0 0. 50 0 0. 13 1. 0 0 0. 25 1. 0 0 0. 5 1. 0 0 1. 0 1.0 0

Example 7 A wet-on-wet coating run was carried out involving X-ray typegelatin photographic emulsion. The ratios of tetra sodium N-(l,2dicarboxyethyl) N-octadecyl sulfosuccinamate to total compositionwere 1. 0, 0.4, 0.2 and 0.1 gram to 2.5 pounds of emulsion and 1.0, 0.5,0.2 and 0.1 gram per 7.7 pounds of gelatin overcoat. The ease ofwet-on-wet coating at high speeds was found to be even better than hasbeen obtained in previous coating experiments using coating aids whichhave been regarded as satisfactory in those operations. The coatingoperation was carried out using a hopper coating technique.

Commonly in multiple coating operations applied simultaneously theconcentration of surfactant in a given layer must be equal to or greaterthan that in the layer below to avoid serious coating defects with thecoating aids as used above. With the coating aids designated hereinsuccessful coating is obtained in simultaneous multiple coatingoperations independent of the concentration ratios of the coating aids(surfactants) in the two contiguous layers. Successful simultaneouscoatings have even been carried out when the surfactant was in the lowerlayer only.

Example8 A wet-on-wet coating operation was carried out in which thecoating aid used was tetrasodium N-(1,2 dicarboxyethyl) N-laurylsulfosuccinamate. The coating aid was used in the emulsion in theproportion of 1 gram to 2.5 pounds of emulsion and 1 gram to 7.7 poundsof gelatin overcoat. The ease of wet-on-wet coating at high speeds wasoutstanding.

Example 9 In a simultaneous application of gelatin silver halideemulsion and clear gelatin overcoat to paper by a hopper technique thefollowing results were obtained wher'f N-(alkyl-i-alkenyl) N-maleylsodium aspartate was used as the coating aid. This coating aid wasprepared by using as the amine in its preparation a commercial productconsisting of a mixture of hexadecyl, octadecyl and octadecenylamineswhich supplies the (alkyl-l-alkenyl) portion of the surfactant:

Cone. of Cone. of Photosurfactant surfactant (7.5 ft?) graphic in emulinovercoat Repel- Propsion (gm./1b.) lencies erties -l 0. 13 0. 13 0 OK.0. 25 0. 13 0 OK. 0. 5 0. 13 O O.K. 1. 0 0. 13 0 OK. 0. 13 0.25 0 OK. 0.25 0.25 0 O.K. 0. 5 0.25 0 O.K. 1. 0 0. 25 0 O.K. 0. l3 0. 5 0 O.K. 0.25 0. 5 0 OK. 0. 50 0. 5 0 OK. 1.0 0. 5 0 O.K. 0. 13 1. 0 0 OK. 0. 251.0 1 O.K. 0. 5 1. 0 0 O.K. 1. 0 1. 0 1 OK.

In a similar run the sodium salt of N-maleyl-N-abietyl aspartic acid wasused as a coating aid. Coatings of good photographic properties and goodrepellencies were obtained.

Example 10 In a dry wet-on-dry application of gelatin silver halideemulsion to paper by a hopper technique the following results wereobtained when the sodium salt of N-malely- N-lauryl aspartic acid wasused as the coating aid:

In a wet-on-wet coating run employing a gelatin photographic emulsion ofthe X-ray type and N-maleyl-N- (a1kyl+alkenyl) aspartic acid, sodiumsalt, as the coating aid, the ease of coating was equivalent to thatobtained with the best coating aids known for this purpose at thepresent time.

In a run similar to the preceding, N-maleyl N-lauryl aspartic acid,sodium salt, was used as the coating aid. The results obtained weresuperior to those which are obtained using coating aids which have up tonow been found to be best for this purpose.

In addition to the compounds having both amide and carboxylic groupstherein in accordance with our invention there has also been someinterest shown in the use of certain sulfonated compounds as coatingaids for the coating out of aqueous gelatin compositions includingphotographic emulsions. For instance, compounds having the formula SOaNaC(CHahCH wherein R represents hydrogen or an alkyl of 1-4 carbon atomsand n=1-18 have been found to be suitable in many situations for use ascoating aids. These compounds prepared by the action of fatty acids onorthophenylene diamine followed by sulfonation thereof have beendescribed. in French Patents 774,018 and 818,919 and. German Patent6335818. These surfactantshave beenfound.

to beuseful as coating aids in the coating out. of. Xeray' emulsionsandin wet-on-wet coating. processes usinglthose emulsions as well as inwet-on-dry processes. Some corn.- pounds of this type useful in coatingoperations. are 2-n.- pentadecylbenzimidazole sodium sulfonateZ-n-tridecyl benzimidazole sodium sulfonate and 2-n-und ecylbenzimidazole sodium sulfonate. These coating aids,.however, havecertain characteristics which render them inferior to the compoundscontaining amide and carboxylic groups in accordance with our invention.

Another type of material which has been of some interest for aiding incoating operations involving aqueous gelatin coating compositions arethe alkylarylguanamin sulfonates, such as those having the structuralformula in which formula R represents an alkyl group of 1-18 carbonatoms and R represents hydrogen or an alkyl group" of 14 carbon atoms.Using a hopper technique these coating aids are superior to saponin inwet-on-wet coating operations. However, both these and the coating aidsreferred to in the preceding paragraph are not useful in all types ofphotographic emulsions. In certain types of photographic emulsions ithas been noted that these coating aids cause a speed loss of 25-30%while in other types of emulsions losses in speed do not occur. Alsowith coating aids ofthe. type of thosediscussed in the last twoparagraphs it is necessary in simultaneous multiple coating operationssuch as described in US. Patent No. 2,761,791 of T. A. Russell that thecoating aid be higher in the overlayer than in the lower layer toproduce a smooth uniform coating in both layers. If the order ofconcentration is reversed a non-uniform flow results which contributesto the obtaining of a coating of inferior characteristics. In contrastthe coating aids of the invention give satisfactory effects when used insimultaneous multiple coating operations of the type described in theRussell patcnt irrespective of the ratio of coating aids used in the twoadjacent layers in that process. Coating aids of the type described andclaimed in this application do not cause desensitization of silverhalide emulsions such as results in the case of certain emulsions whenalkylaryl guanamin sodium sulfonates and the benzimidazole sulfonatesare used as coating aids therein.

We claim:

1. A photographic element comprising a support and a light-sensitivesilver halide emulsion layer, said element having a gelatin overcoatlayer upon the emulsion layer, one of which layers contains a smallamount of a compound selected from the group consisting. of thecompounds having the following structural formulas:

C J HCOOX CHCOOX RNOHCOOX SOsX CHzCON-R OHQOOOX IHC'OOX SOaX in whichformulas R is an alkyl radical of at least. 8-carbon atoms and X is analkali metal substituent,

2. A photographic element comprising a support and a light-sensitivesilver halide emulsion layer, said element having over the emulsionlayer a gelatin overcoat layer, one of which layers contains a smallamount of a com- CH2OONHR CHOOOX in which R is an alkyl radical of atleast 8- carbon atoms and X is an alkali metal substituent.

3. A photographic element comprising a support and a light-sensitivesilver halide emulsion layer, said element having over the emulsionlayer a gelatin overcoat layer, one of which layers contains a smallamount of a compound having the formula:

CHzOOOX OHCOOX CHzCON-R (IJHCOOX in which R is an alkyl radical of atleast 8 carbon atoms and X is an alkali metal substituent.

4. A photographic element comprising a support and a light-sensitivesilver halide emulsion layer, said element having over the emulsionlayer a gelatin overcoat layer, one of which layers contains a smallamount of a compound having the formula:

O=CCH=GH(JOOX RNCHCOOX CHzCOOX in which R is an alkyl radical of atleast 8 carbon atoms and X is an alkali metal substituent.

5. A photographic element comprising a support and a light-sensitivesilver halide emulsion layer, said element having over the emulsionlayer a gelatin overcoat layer which layers contain a small amount ofN-octadecyl disodium sulfosuccinamate.

References Cited in the file of this patent UNITED STATES PATENTS2,252,401 Jaeger Aug. 12, 1941 2,383,130 Jaeger et al Aug. 21, 19452,438,092 Lynch Mar. 16, 1948 2,527,260 Hart et al Oct. 24, 19502,739,891 Knox et al Mar. 27, 1956 2,823,123 Knox et al Feb. 11, 19582,843,487 Knox et al July 15, 1958 OTHER REFERENCES Schwartz et al.:Surface Active Agents and Detergents, pp. 732-733, vol. II (1958),Interscience Publishers Inc., New York.

Websters New International Dictionary, p. 1067, item glue, 1956 ed.,Merriam Co. Publishers, Springfield, Mass.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,992,108 Jill 11, 1961 William J. Knox, Jr., et al.

ified that error appears in the above numbered pat- It is hereby cert onand. that the said Letters Patent, should read as ent requiring correcti"corrected below. 1

Column 8, line 7, after "oom" insert the following line: pound havingthe formula:

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. {LADD Commissioner ofPatents USCOMM-DC-

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND A LIGHT-SENSITIVESILVER HALIDE EMULSION LAYER, SAID ELEMENT HAVING A GELATIN OVERCOATLAYER UPON THE EMULSION LAYER, ONE OF WHICH LAYERS CONTAINS A SMALLAMOUNT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE COMPOUNDSHAVING THE FOLLOWING STRUCTURAL FORMULAS: